Hello,i have 1991 MB 300e with automatic climate control.the problem is when i have the heater on while the light is On too the climate control is shinning for 20min and then it slowly dimms and the light goes off but the heater works without a problem.when i switch the car off and then start it again the light on the climate control works again for 20 min and then dimms and afterward dies again.
but if i am driving with the heater off the light is always shining it doesnt go out.
pls.help

Of course try 2 new bulbs first.

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thank u for ur reply.could it be only the bulbs??????

Yes.
Start simple = replace the bulbs first..

Note:
If an aftermarket radio has been installed, verify the power and/or ground is NOT connected to the lighting or climate control circuit.






Have a great day.

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Gentel men thank u for ur help.i changed the bulbs but no change sfter 20min with the heater on the bulbs dimmed and then went out.after i restarted the cac they went fine for 20min.
As for the radio it was installe ten years ago and never had any problem.
So whats next i wonder???????